There sure isn’t much information out there on cantilevered necks (a.k.a. elevated fingerboards) and how to build them. I haven’t been able to find anything on it. I’m really looking for a step-by-step detailed documentation, preferably including pictures of the process. Anyone have anything to add to this?

I've been using a cantilevered neck on my last four builds and I'm sold. I find several advantages: separate adjusting of the neck angle and the fretboard height, both at build time and later, which allows independent string height and playing action, the freeing of the upper bout, and more.

My approach has a couple of limitations which some folks may not like and provides opportunity for some structural changes which, I feel, have advantages, but aren't required. Here's what I do:

First, I build the neck, using a neck heel with parallel sides. I use a bolt-on neck accessed via the soundhole. I use a heel with parallel sides about 2" wide, positioning the face that will contact the headblock about 4" from the end of the neck shaft (all pieces rectangular, sanded/planed on 4 sides -- no taper in the neck shaft at this point).

I use a headblock which is at least an inch wider than the heel and is flat in the area where the heel of the neck will contact it. I cut the bent and profiled guitar sides perpendicular to their top edge and glue them to the headblock with enough space between them that the face of the heel (which has parallel sides) just fits between the ends of the two guitar sides. This forms a shallow mortise that allows the neck to sit flat on the headstock without constraining the neck's position relative to the future soundboard. I then glue the other end of each side to the tailblock.

At this point I continue to work on the neck. I've tried an adjustable truss rod with access at the headstock and one with access at the end of the fretboard, but have settled on using two carbon fiber bars under the fretboard as the most satisfactory solution for neck reinforcement. Any future change in relief, action, etc. can be accommodated by adjustment of the neck angle, position, or both. I then complete the shaping and carving of the neck, taking care not to modify the heel within ⅛" of the face that will contact the neckblock. I make sure that the heel is longer than the "thickness" of the guitar at the neckblock. As I will be thinning the wood that forms the neck shaft in the area between the heel face and the end of the fretboard, I need to carefully carve the sides of the neck shaft to preserve the width of the heel up to 1/16" below the fretboard.

After the neck is finished and the body is complete, I attach the neck to the body with a single ¼" x 20 bolt through a hole in the headblock which is ¼" wide and ⅜" to ½" high, allowing significant adjustment. I've used a 90 degree angle between the neck heel and the fretboard, and find that, with the 30' radius I use on the top and the with the top of the fretboard about 7/16" above the soundboard, this gives good projection of the fret surface to the top of the bridge with minimal adjustment. If an angle adjustment is needed, either while building or for later adjustment, a small wedge (a la Taylor) addresses the issue. I cut the end of the fretboard extension (and supporting neck shaft) to follow the edge of the soundhole. I cut the end of the neck heel to allow a cap flush with the guitar back.

I mentioned other advantages (at least I think they're advantages) to this build process. One is the freeing of the upper bout because the fretboard isn't laying on it or glued to it. But if the soundboard is braced with a massive upper transverse brace then an elevated fretboard won't make that much difference. So I've been avoiding use of a UTB and have been providing structure to the guitar via interior bracing. I fit mahogany blocks (similar to the headblock) to the inside of the waist and run significant (e.g., ¾" x ¾") braces from the headblock to the waist blocks and similar braces from the waist blocks to the tail block. Then I brace the top using X-bracing that is let into the waist blocks. The interior braces are parallel to the soundboard but clear all soundboard braces by at least ⅛". I'm still experimenting with techniques for bracing the soundboard's upper bout, but they are tone related, not structure driven. The upper bout in these guitars is definitely active; it moves against fingertips when the strings are played. I like the effect on tone; it's rich and complex.

I hope this description makes sense. Post a question or PM me if I can clarify.

I found this luthier’s site and he makes an elevated fingerboard (very similar, if not the same as a cantilevered neck): http://byersguitars.com/2015/10/13/elev ... ck-design/. I noticed he uses a workboard that tapers up to match the angle of the cantilevered neck. My only problem with this is that it looks like the rest of the workboard is flat, which would make the soundboard flat. I use a 28’ radius on tops, so it would be difficult to find a mix of the two, although I’m sure there is some way that a dish with a compound radius could be made by CNC.

I found this luthier’s site and he makes an elevated fingerboard (very similar, if not the same as a cantilevered neck): http://byersguitars.com/2015/10/13/elev ... ck-design/. I noticed he uses a workboard that tapers up to match the angle of the cantilevered neck. My only problem with this is that it looks like the rest of the workboard is flat, which would make the soundboard flat. I use a 28’ radius on tops, so it would be difficult to find a mix of the two, although I’m sure there is some way that a dish with a compound radius could be made by CNC.

Greg Byers is one of the giants among classical builders, IMO. I believe he builds with a domed top.

Usually the workboard is slightly dished and contacts the top mainly at the perimeter. The dish is deep enough to clear the dome. Work done on the dome is often done on a separate dish.

_________________formerly known around here as burbank_________________

I have done 2 and love the result. I use cantilever as I wanted the fingerboard floating and it allows the top more active area. I did not like the look of the added on piece from the heel to the fretboard end so use a scarf joint stacked heel layout. It took a bit of thinking to figure it out but the result is great.

A cantilevered neck is very similar to an archtop neck. Bob Benedetto's archtop building book would be a good reference for construction of one. I have his set of VCR tapes that go along with the book that I would be willing to part with if you are interested.

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